FR3039172A1

FR3039172A1 - ACOUSTIC ENROBE WITH MULTIPLE DISCONTINUITIES AND POROSITIES FOR CIRCULATION PATHWAY

Info

Publication number: FR3039172A1
Application number: FR1556908A
Authority: FR
Inventors: Francois Olard; Simon Pouget
Original assignee: Eiffage Travaux Publics SAS
Current assignee: Eiffage Travaux Publics SAS
Priority date: 2015-07-21
Filing date: 2015-07-21
Publication date: 2017-01-27
Anticipated expiration: 2035-07-21
Also published as: FR3039172B1

Abstract

L'invention vise à fournir un nouvel enrobé acoustique pour voie de circulation comprenant au moins un liant, de préférence un liant bitumineux, et des granulats comportant plusieurs fractions granulaires d/D, définie chacune par un calibre inférieur (d), un calibre supérieur (D) et par une médiane dm, caractérisé en ce que la distribution des fractions granulaires des granulats est telle que sont définies au moins deux discontinuités granulaires. L'invention a également pour objet le procédé de fabrication de cet enrobé, ainsi que la voie de circulation le comprenant.The aim of the invention is to provide a new traffic lane acoustic coating comprising at least one binder, preferably a bituminous binder, and aggregates comprising several granular fractions d / D, each defined by a lower caliber (d), a higher caliber (D) and by a median dm, characterized in that the distribution of the granular fractions of the aggregates is such that at least two granular discontinuities are defined. The subject of the invention is also the method of manufacturing this mix, as well as the circulation path comprising it.

Description

ACOUSTIC ENROBE WITH MULTIPLE DISCONTINUITIES AND POROSITIES

FOR CIRCULATION

Field of the invention The invention belongs to the technical field of public works, and more particularly to the construction of traffic lanes.

More specifically, the invention relates to an acoustic mix intended to be integrated into the structure of a traffic lane. Such a mix is of the type comprising a binder, preferably bituminous, and aggregates whose granulometric distribution makes it possible to define pores of different sizes and targeted within the mix, giving it an improved acoustic absorption capacity. The invention also relates to the method of manufacture of this mix, as well as the traffic lane comprising it.

Technological background of the invention

The traffic routes considered here are road and motorway pavements as well as railways or industrial, port or airport platforms.

Roadway means a structure consisting of at least one upper layer called road surface (itself including a wearing course and a tie layer), and at least one lower layer.

Traffic lanes, and in particular pavements, are formed by bituminous mixes in which the aggregates are generally bonded to each other by bitumen.

Aggregates are a set of mineral grains called fillers, sand, sand, chippings, gravels or ballasts depending on their size.

There are six main granular classes, each denoted by / D 'with d'<D'and corresponding to an interval of grain sizes with d corresponding to the extreme dimension (caliber) lower and D' to the extreme dimension (caliber) higher. Dimension means the largest dimension of the grain. These six classes are the following: - fillers 0 / D 'with D'<2 mm and at least 70% passing through a sieve of 0.063 mm, - sablons 0 / D 'with D' = 1 mm, and less than 70% passing through a sieve of 0.063 mm; - the sands 0 / D 'with 1 <D '<6.3mm; - the bass 0 / D 'with D'> 6.3 mm; - chippings of / D 'with d = 1 mm and D' = 125 mm; - ballasts of / D 'with d = 25 mm and D' = 50 mm.

The structure and composition of pavement pavements are important because of their impact on the noise generated by vehicular traffic on the roadway. The noise pollution related to traffic is more or less important depending on the speed and flow of traffic, or the location of roads compared to inhabited areas.

The rolling noise, which is created at the level of the tire-road contact, is mainly caused by two phenomena: - the impact of the tires on the road surface: when a tire rolls on a surface that is not perfectly smooth, the irregularities indirectly cause vibrations of the sides of the tire. However, only sufficiently deep and wide irregularities (typically greater than 1.5-2 cm in size) cause vibrations. Reducing the size of aggregates on the road surface reduces the depth of irregularities. The vibratory processes are more particularly involved in the low and medium frequency range (approximately 80 Hz to 120 Hz). - the phenomenon of "air pumping": a tire that rolls on a surface produces noise related to the compression then the sudden relaxation of the air trapped in the cells of the tires, which is accompanied by a "suction effect"". This phenomenon, which is dominant for noise emission in the high frequency range (approximately 1 to 5 kHz), is all the more important as the contact area between the tire and the roadway is important. This phenomenon is largely attenuated on a surface which has small asperities (typically less than 1 cm) or a good porosity related to the presence of surface holes communicating with the voids present in the structure of the coating, which will facilitate the circulation air. These connected voids absorb not only tire-road contact noise but also engine noise as well as other environmental noise. These voids are generated by the granulometric distribution of aggregates, determined by sieving analysis according to EN 933-1. To date, several types of acoustic road surfaces are present on the market: • Draining bituminous concrete:

These are bituminous concretes whose particle size has a discontinuity, which is characterized by the absence of a fraction of aggregates and a large volume of voids of at least 20%.

In this case, the noise reduction is based on the fact that the coating has many voids.

Their thickness is generally greater than 4 cm. • Asphalt mixes with thin or very thin layers:

There is a marked trend towards the development of thin-film coatings, the limited amount of materials required for their manufacture making these coatings both financially attractive and easier to renew. Thin-film mixes generally have a void percentage of between 6% and 13%, while very thin-layer mixes typically have a percentage of between 12% and 25%. There are sub-families of thin mixes with specific acoustic qualities, such as discontinuous thin bituminous concrete. This is a 2 to 3 cm layer characterized by a fairly high percentage of chippings (around 70%). This bituminous concrete has a particle size discontinuity, resulting from the absence of a particle size fraction to promote the creation of interstices, thereby improving the porosity of the coating, and therefore its performance in terms of sound absorption. The addition of elastomers or cellulose fibers in the binder makes it possible to retain good mechanical properties, despite the thinness of the layer. • Coatings containing synthetic resin as binder:

These are coatings composed of a layer of resinous binder, covered with aggregates of very small particle size (typically 2/4), thus having no porosity. Their anti-noise properties are based on the reduction of noise emission, but not on absorption, unlike other types of acoustic mixes. This type of material has the advantage of being very resistant, and therefore can be used at critical locations (sharp corners, intersections ...), with high and durable anti-slip qualities. Their implementation nevertheless remains expensive.

The patent application FR2900165A1 describes a composition with anti-noise properties for upper layers of pavements comprising a granular mixture and at least one binder, characterized in that the granular mixture satisfies the following conditions: a) 70 to 100% by weight of the constituents of the mixture granular have dimensions less than 3.15 mm; b) 45 to 100% by weight of the constituents of the granular mixture have dimensions less than 2 mm; c) 3 to 20% by weight of the constituents of the granular mixture have dimensions less than 1 mm; d) 2 to 10% by weight of the constituents of the granular mixture have dimensions less than 0.063 mm.

In particular, this application describes as an example a granular mixture obtained from 48% of aggregates with a class of = 2 / D '= 4.48% aggregates of sand of class = 1 / D' = 2 and 4% filler. This granular mixture, which has a particle size discontinuity between 63 μm and 1 mm, lacks mechanical stability, due to the presence in the mixture of aggregates of small and coarse aggregates equally.

The patent application FR2958302A1 describes a high performance hydrocarbon asphalt for road surfaces. This mix has the advantage of being self-compactable, so more economical implementation. The aggregates of the mixes disclosed in FR2958302A1 have a particle size distribution having two discontinuities, as is apparent from Table 1 below.

Table 1. Examples of compound composition and compaction performance of high performance asphalt compaction with double granular discontinuity

The first discontinuity of the "HP6 skeleton" and "HP7 skeleton" granules of the mix according to FR2958302A1 results from the absence in the aggregates of a granular fraction d = 2 / D = 6. The second discontinuity of the "HP6 skeleton" and "HP7 skeleton" aggregates results from the absence in the aggregates of a granular fraction d = 6 / D = 14 and a granular fraction d = 10 / D = 14.

This mix has a very low void percentage, and therefore has no anti-noise properties.

In this context, it has appeared useful to seek to improve existing mixes, to achieve a mix formulation that is inexpensive and easy to implement, while having a high sound absorption capacity, and a mechanical strength sufficient and durable.

Objectives of the invention

Thus, the invention aims to improve the acoustic performance of the prior art mixes, and in particular to meet at least one of the following objectives: - Provide new acoustic mixes, allowing absorption of rolling noise, c ' that is, having a high sound absorption coefficient, in a frequency range from 40 Hz to 4000 Hz; - Provide new acoustic mixes, which leave the possibility to their manufacturer, to target one or more particular frequencies of the noise to absorb, by deliberately modulating the granulometry of the aggregates; - Provide new acoustic mixes to limit noise emission in pneumatic-pavement contact; - Provide new acoustic mixes with adequate mechanical properties and durability, especially in terms of resistance to rutting (ie the accumulation of permanent deformations under traffic), giving it a long life; - To provide new asphalt mixes with improved and long-lasting anti-noise properties, while retaining all the performance normally expected for asphalt, for example, wearing course: mechanical strength whatever the traffic, good adhesion for tires especially in wet weather, eco-compatibility, satisfactory aesthetic appearance and ease of implementation; - Propose a process for manufacturing new acoustic mixes, which is easy to implement, both in terms of manufacturing and application, and inexpensive; - Provide a taxiway with acoustic asphalt, which is easy to manufacture, inexpensive, and has significant noise abatement capability, without prejudice to its mechanical properties, adhesion properties, durability nor its eco-compatibility.

Brief description of the invention

These objectives, among others, are achieved by the present invention, which relates, according to a first aspect, to a roadway acoustic coating comprising at least one binder, preferably a bituminous binder, and aggregates comprising a plurality of granular fractions d / D. , each defined by a lower caliber (d), an upper caliber (D) and a median dm; characterized in that the distribution of the granular fractions of the aggregates is such that: i. for at least a part of the so-called continuous granular fractions, on the one hand, the medians progressively increase from a fraction da / D "of smaller median dm", followed by a fraction dp / Dp, up to a fraction d® / D® of greater median dm®, and, on the other hand, the mass ratios Rm of these fractions, defined with respect to the total weight of the aggregates, also increase progressively since the fraction d ° 7Da more small median dm "up to the fraction d® / D® of greater median dm®, the ratio Rm® / Rm6 being greater than or equal to 2, preferably to 3, and more preferably still to 4; ii. at least two other granular fractions, called rupture fractions, are each inserted between two continuous granular fractions, these granular fracture fractions being respectively da / Da of median dma and db / Db of median dmb greater than dma, the mass ratio of each fraction of rupture being lower than the mass ratio of the preceding continuous fraction, and the granular fraction da / Da of median dma between the fraction d ° 7Da and the second continuous fraction dc / Dc has a mass ratio Rma lower than Rm ".

The presence of at least two granular fracture fractions within the mix leads to the creation of vacuum, of at least two different sizes, since the absence of a granular fraction prevents filling of certain interstices left empty between grains in contact if the ratio Rn ^ / Rm6 defined above is respected.

In addition, the ratio Rm "/ Rm greater than or equal to 2 means that there is in the presence in the aggregates of a predominantly predominant portion of large grains, resulting in a significant percentage of void, preferably greater or equal to 20% within the mix.

The combination of these two characteristics gives the mix according to the invention improved acoustic absorption properties.

It is the merit of the inventors to have introduced into the mix the presence of at least two void sizes to absorb at least two soundtracks centered on different absorption frequencies. Thus, depending on the discontinuities that the user chooses to introduce into the granular mixture before manufacture of the mix, it is possible thanks to the present invention to target in advance the frequency of the sound absorbed. This may represent a particularly advantageous characteristic of the present invention, the user being able to choose to absorb rather serious and / or rather acute sounds, depending on the noise present in the environment of the lane intended to be equipped with the acoustic coated according to the invention.

The fact that the granular fraction da / Da of median dma has a mass ratio Rma lower than the mass ratios of the continuous granular fractions Rm1 (β <i <co) gives the asphalt at least two advantages: - economy in manufacturing, since less binder is required to coat large aggregates than sand; By way of example, if we compare the "material" prices per ton of a conventional acoustic mix (Microphone® Boitron) to an innovative mix according to the invention (BBDD 0/6 Boitron), a gain is observed. significant in favor of the BBDD 0/6 of the order of 10%: * Microphone® Boitron (= 56.5 €): + Aggregates (94.6%): order of magnitude of about 20 € / ton + Modified bitumen (5.4%) : order of magnitude of about 700 € / ton * BBDD 0/6 Boitron (* 51.5 €): + Aggregates (95.4%): order of magnitude of about 20 € / ton + Modified bitumen (4.6%): order of size of about 700 € / ton - a mechanical strength allowed by the multiple contacts between coarse aggregates. The subject of the invention is also a method for manufacturing an acoustic mix according to the invention comprising the following steps: a- choosing the aggregates classes d / D so that the distribution of the granular fractions after mixing is as defined above, b- optionally selecting at least two target acoustic absorption frequencies for the asphalt mix and choosing the aggregates classes d / D such that the granular fracture fractions obtained after mixing allow the coincidence of the absorption peaks. (measured according to standard NF EN ISO 10534-2 of 2003) with the target sound absorption frequencies according to the thickness of implementation aimed, c- to mix the aggregates in order to obtain a homogeneous whole, d- to add a binder, preferably a bituminous binder, e-mix the aggregates with the binder.

Another object of the present invention is a circulation route comprising at least one acoustic asphalt layer according to the invention, said layer preferably being an upper road layer, and even more preferably a wearing course. Definitions

Throughout this presentation, any singular denotes indifferently a singular or a plural.

The definitions given below as examples may be used in the interpretation of this paper.

"Aggregates" means a set of mineral grains constituting the framework of the mix and connected to each other by the binder in the mix.

By "granular fraction" is meant all grains passing between two sieves of different mesh sizes of / D ', when carrying out a particle size analysis according to EN 933-11.

By "mass ratio Rm" denotes the mass percentage of a granular fraction d / D, based on the total mass of aggregates.

By "median dm" of a granular fraction is meant the value for which 50% of the weight of aggregates of the granular fraction considered are smaller than dm.

Continuous granular fractions are denoted by d1 / D1, with i varying in increasing order according to the order of the letters of the Greek alphabet (i = α, β, γ, ..., ω).

DETAILED DESCRIPTION OF THE INVENTION The invention will also be better understood from the attached drawings in which: FIG. 1 is a diagram illustrating the particle size distribution of an acoustic mix according to the invention; FIG. 2 is a general view; of a roadway comprising a wearing course based on an acoustic mix according to Figure 1, - Figure 3 is a detailed plan view of the mix of Figure 2, - Figure 4 is a graph. showing the evolution of the acoustic absorption coefficient of the control mixes as a function of the wavelength, and - Figure 5 is a graph showing the evolution of the acoustic absorption coefficient of the mixes according to the invention as a function of the wavelength.

As shown in FIG. 1, the aggregates comprise at least two granular fracture fractions da / Da and db / Db, and at least three continuous granular fractions da / D ", dp / Dp and d, l / D,! , each fraction being defined by a lower caliber (d) and a higher caliber (D). Typically, in the embodiment shown in FIG. 1, D® serves as the upper limit of the aggregates sizes, the portion of aggregates exceeding the D® caliber being very low in the sense of the standards EN 13043 and EN 933-1.

The aggregates used in the mix according to the invention are solid fragments made from new materials or recycled materials. New aggregates are either natural from gravel pits or quarries, or artificial from foundry slag for example. Recycled aggregates come, for example, from the milling of asphalt courses, the crushing of asphalt slabs, the waste or pieces of asphalt slabs and the surplus asphalt production.

The residual quantity of aggregates in each of the fracture fractions is in particular the result of successive industrial or sieving laboratory operations known in the art, which have certain imperfections or tolerances (see standard EN 933-1).

In a preferred embodiment of the invention, the upper gauge D "of the continuous fraction d ° 7Da is equal to the lower caliber da of the fracture fraction da / Da. Thus, in this preferred embodiment, and as shown in FIG. 1, the first continuous fraction d 1 / Da is directly followed by the first break fraction da / Da.

In a specific embodiment, the ratio between the mass ratio of each of the granular fracture fractions relative to its relative width is such that:

preferably 0.3, and even more preferably 0.2;

And

preferably 0.4, and even more preferably 0.3.

It is the merit of the inventors to have determined that this ratio could be related to the relative width of the granular fracture fraction considered by the following formula:

Indeed, it is important to define the fracture fractions with respect to this ratio between the mass ratio relative to the relative width of the fraction, this ratio to be sufficiently low to ensure a real discontinuity in the mix.

In a specific embodiment, the acoustic mix according to the invention is characterized in that the continuous fraction d ° 7Da has a higher gauge D "determined according to standard NF EN 933-1, less than or equal to 4 mm, preferably 2 mm, and even more preferably 63 μm. This fraction of / Da is derived from a granular class comprising fines, for example with D '= 63 μm.

In another specific embodiment, the acoustic mix according to the invention is characterized in that the fracture fraction da / Da has, on the one hand, a caliber less than or equal to 63 μm and, on the other hand, an upper caliber Da greater than or equal to 4 mm, preferably 2 mm, and even more preferably 1 mm, as determined according to standard NF EN 933-1. This da / Da fraction comes from a granular class comprising a sand, for example with d = 1 mm and D '= 2 mm.

In a preferred embodiment, the acoustic mix according to the invention is characterized in that the continuous fraction d® / D® defined by the median dm® has a higher caliber D® less than or equal to, in a rising order of preferably 25 mm, 14 mm, 10 mm, 6 mm.

Advantageously, the mass ratio of the continuous fraction d® / D® is greater than or equal to 50% by weight, preferably 60%, even more preferably 70% by weight relative to the total of the aggregates.

The presence of a large number of large aggregates associated with the presence of fracture fractions allows a low density but stable stack. Thus, the acoustic mix has a high void percentage, essential characteristic to obtain improved anti-noise properties, while having a high mechanical strength.

FIG. 2 shows a roadway 50 according to the invention, the structure of which comprises from bottom to top: - a layer of form 51 resting on the ground 56, - a base layer 5 situated above the layer of form 51, said base layer 5 being optionally subdivided into a foundation layer 5a and a base layer 5b, and a surface layer 53 located above the base layer 5 and having an upper surface capable of receiving the traffic and the rolling of the vehicles, said surface layer possibly being subdivided into a connecting layer 55 and the wearing course 54. The roadway structure 50, and particularly the wearing course 54, must support a plurality of solicitations: 30 - direct mechanical stresses resulting from the rolling loads of vehicle traffic, - thermo-physical stresses generated by temperature variations and the effects of freezing, also called thermal stresses. es, 35 - chemical stresses exerted by fluids spread over the road surface, in particular rainwater, vehicle emissions (exhaust emissions, loss of oil and fluids), de-icing salts and even objects or fluids accidentally dropped on the roadway. The roadway, and in particular the wearing course 54 must have sufficient mechanical characteristics to prevent the formation of ruts and cracks and thus ensure satisfactory durability of the roadway.

The Applicant has developed a particularly advantageous hydrocarbon coating concerning its anti-noise properties and its mechanical strength, while having a very attractive cost, intended in particular to obtain the wearing courses 54, but which can however also be used. for the tie layer 55 of the surface layer 53.

Thus, after placing the asphalt and compacting on its support, a structure as shown in FIG. 3 is obtained. The coarse aggregates 20 belonging to the granular fraction d07D0) are in contact with aggregates of the same fraction. because the aggregates of the intermediate size (fracture fraction) are not or little present. The aggregates 21 belonging to the fraction dp / Dp and the aggregates 22 belonging to the fraction da / D "are housed between the gaps 4 between the coarse aggregates 20, without preventing them from coming into contact with each other. The hydrocarbon binder 3 coats well the entire surface of the aggregates. The presence and the good distribution of the binder 3 confers good mechanical strength to the asphalt thus obtained.

Moreover, Figure 3 illustrates the percentage of relatively large vacuum within the mix. In particular, the acoustic mix according to the invention advantageously has, after compacting, a void percentage greater than or equal to 20%, preferably 25%, even more preferably 30%, defined according to the standards EN 12697-8 or the standard EN 12697 -31 to 25 gyrations.

Preferably, the mix according to the invention has a percentage of rut depth at 10,000 cycles, measured according to the standard 12697-22 at 60 ° C, less than or equal to 10%, preferably 7.5%, and even more preferentially 5%.

Figure 3 also shows the presence within the mix of at least two vacuum sizes for improved acoustic absorption. The presence of at least two fracture fractions within the mix leads to the acoustic absorption of at least two main frequency bands, the central frequency of which can be determined in advance by the manufacturer according to the aggregates present in said fractions. a break.

Thus, in a preferred embodiment, the acoustic mix according to the invention has an acoustic absorption coefficient whose values include at least two local maxima (absorption peaks) greater than 0.7, preferably 0.8 , still more preferably 0.9, over a frequency range between 40 and 4000 Hz, and measured according to the NF standard in ISO 10534-2 / 2003.

In another specific embodiment, the binder content is less than or equal to 5.5% by weight, preferably 5%, even more preferably 4.7%, and more particularly 4.5%. The relatively small proportion of binder present in the mix gives it a moderate cost.

According to a preferred embodiment of the invention, the binder is of a bituminous nature. For the purposes of the present invention, a "bituminous binder" designates a bituminous compound chosen from among pure, multi-graded or modified air-modified bitumens or mixtures thereof, and capable of bonding granular materials to one another. The bituminous binder according to the invention is generally a mixture of natural hydrocarbonaceous materials derived from the heavy fraction obtained during the distillation of petroleum, or coming from natural deposits in solid or liquid form, with a density generally of between 0.8 and 1.2. It can be prepared by any conventional technique. Are admitted as bituminous binders within the meaning of the invention the pure bitumens defined in standard NF EN 12591, such as bitumens of class 160/220, 100/150, 70/100, 50/70, 40/60, 35 / 50, 30/45 or 20/30, without limitation. These standard classes correspond to ranges of penetrability at 25 ° C determined according to the method EN 1426 and are expressed in 10'1 mm.

More preferably, the binder is a modified bitumen, preferably an agent selected from the group consisting of, ideally consisting of: natural rubbers, synthetic polymers, organo-metallic compounds, sulfur and sulphides, additives allowing to limit the clogging of draining mixes (for example, Siloxane or Silane families), tackifying dopes, and mixtures thereof. More generally, the modified bitumens are defined in standard NF 14023, for example modified bitumens by incorporating additives of any kind such as additives in order to improve the adhesiveness characteristics or the mechanical strength under high traffic. or aggressive, or to artificially provide the properties necessary for cationic emulsification. Mention may be made of bitumens improved by incorporating organic or mineral fibers, in particular glass, carbon or cellulose fibers, by incorporation of synthetic or natural elastomers of the rubber powder (polybutadiene, styrene-butadiene rubber or SBR) type, copolymers of ethylene and vinyl acetate (EVA), random or block copolymers of styrene and conjugated dienes, for example SBS block copolymers, by incorporation of thermoplastics such as, for example, polyolefins (polyethylene, polypropylene), polyamides and polyesters, or by incorporation of thermosetting resins such as epoxy resins (bitumen / epoxy binders) or polyurethane resins. It is also possible to use mixtures of bitumens of different types.

Of course, the composition according to the invention may comprise mixtures of binders belonging to the various categories mentioned.

According to an advantageous embodiment of the invention, the circulation route, as represented in FIG. 2, comprising a bituminous layer according to the invention may comprise a surface layer comprising at least two superimposed sub-layers, a top layer of rolling stock and a lower bonding sub-layer, at least one of said sub-layers being based on at least one asphalt mix according to the invention. Other aspects, objects and advantages of the invention will appear on reading the following nonlimiting examples of several embodiments of the invention.

Examples

Raw materials

The following table (Table 2) gives the granular skeletons of: - four control mixes of the prior art (Microphone ®, Nanophone ® and Nanosoft ®, and - four mixes according to the invention (BB 0/6 DD and BB0 / DD).

Table 2

The BP binder is a 35/50 pure bitumen from the BP Lavera refinery, and the BM binders are SB SB polymer modified bitumens.

The amount of binder can also be characterized by the notion of richness module K explained below.

First, we introduce the concept of specific surface of aggregates, denoted E and expressed in m2 / kg, that is to say the developed surface that would have granules assimilated to spheres. For a given granulometric mixture, the following formula gives an approximation of the specific surface area Σ: Σ = (0.17 G + 0.33 g + 2.3 S + 12 s + 135 f) / 100, with G : percentage of large chippings (diameter> 11mm) g: percentage of small chippings (6 / 11mm caliber) S: percentage of coarse sand (0.3 / 6mm caliber) s: percentage of fine sand (0.08 / 0 caliber, 3mm) f: percentage of filler (diameter <0.08mm).

This equation can be approximated by: Σ = (0.25 G + 2.3 S + 12 s + 150 f) / 100, with G: percentage of coarse gravel (size> 6.3) S: percentage of coarse sand (0.25 gauge) /6.3) s: percentage of fine sand (0.063 / 0.25 gauge) f: percentage of filler (diameter <0.063), which can be further simplified by approximation as follows:

The optimum binder content, denoted 'P', a function of the specific surface area of the aggregates, is given by the following experimental formula

: with: P: binder content (%) a: factor depending on the type of aggregates (2.65 / density of aggregates) Σ: specific surface area of aggregates (m2 / kg) K: richness module K generally varies from 2 , 75 for mixes giving the maximum resistance to deformation, to 3.5 for the most flexible mixes. Measurement methods> Acoustic absorption

The sound absorption measurements will be made according to the so-called impedance tube (or Kundt tube) method. It is used a tube of diameter 46 mm; with a frequency range from 50 to 4300 Hz with transmission measurement (tube modified with a third microphone position behind the material allowing the determination of the intrinsic parameters of the material).

On this tube, a quarter-inch B & K type 4178 microphone, equipped with a B & K type 2633 preamplifier, is used, and can be placed in several positions on the top of the tube, and in a position at its end.

These different positions naturally allow the determination of the acoustic absorption coefficient (and the reflection coefficient), but also the measurement of the transmission coefficient, the measurement of the dynamic density and that of the dynamic incompressibility module.

The Kundt tube loudspeaker is powered by a B & K type 2706 amplifier. A B & K type 2690 amplifier processes the signals received by the microphone. Finally, a National Instruments NI PXI-1031 board generates the input signals.

The measurement of the sound absorption coefficient is carried out thanks to two microphone positions (this method, referred to as the transfer function, is defined in the NF standard in ISO 10534-2, 2003).

By measuring the transfer function between the two abscissa microphones x \ and -U ^ _ p (x2) (nn -: r, we obtain the sound absorption coefficient at normal incidence at P \ xi) which is:

ω with k ~~ T (6'océlité of acoustic waves in the air). ω = 27 / represents the co-pulsation and / the frequency in Hz. 5 represents the distance between the two microphones.

> Actual density MVR

It is measured according to standard NF EN 12697-5. > PCG rotary shear press compaction test (EN 12697-31)

This test is characterized by determining the evolution of the percentage of voids of a predetermined quantity of asphalt subjected to an axial force of 0.6 MPa at an angle of 1 °. This test makes it possible to calculate the compactness or content of voids with n girations (thus the percentage of voids). The PCG test reflects the handling of the asphalt mix which is an important factor since it reflects the ease of implementation of asphalt on site. > Gamma bench The application of standard NF EN 12697-7 makes it possible to measure the apparent density MVA (in Mg / m3). > Rutting test (EN 12697-22)

The susceptibility of a bituminous material to deformations is understood by measuring the rut depth generated by the repeated passage at a frequency of 1 Hz, a rolling load of 0.60 MPa at a temperature of 60 ° C. > Sensitivity to water: Duriez test (EN 12697-12)

A set of test pieces is made and separated into two equivalent batches according to the apparent density of each of the test bodies. It is determined by geometric measurements, six diametric measurements and 4 height measurements, and weighing.

The first batch is kept dry at 18 ° C while the other is saturated with water and kept in a bath at 18 ° C for seven days. The sensitivity to water is determined by the ratio of the compressive strengths of the batch preserved in water (r or Cw) with those of the batch kept dry (R or Cd) and is expressed as a percentage. Results

Table 3 shows the results obtained on the control mixes, while Table 4 shows the results obtained on the mixes according to the invention.

Table 3: Mechanical properties of the control mixes

Table 4: Mechanical properties of the mixes according to the invention

The comparison between Table 3 showing the mechanical results obtained on the control mixes and Table 4 showing those obtained on the mixes according to the invention mainly show that: - In terms of resistance to rutting, the mixes according to the invention exhibit significantly improved values compared to the Nanosoft ® control mix, which has a granular discontinuity alone. It is thus demonstrated that despite a high void percentage, the structure of the mix according to the invention is such that the passage of heavy loads on a traffic lane comprising it, causes little deformation of the pavement; - Similarly, despite a high percentage of voids, including communicating voids (compared to the Nanosoft® control mix), the mixes according to the invention have a good water resistance. The invention therefore fulfills the objective of providing new mixes with significantly improved and durable mechanical properties.

In parallel with this demonstration of the mechanical properties of the mixes according to the invention, FIGS. 4 and 5 allow a comparison between the evolution of the acoustic absorption coefficient of the mixes according to the invention (FIG. 5) and single control mixes. discontinuity (Figure 4).

This comparison shows that the mixes according to the invention: - on the one hand, have significantly improved acoustic absorption values, thus demonstrating the effectiveness of their use in road environment, - on the other hand, present at least two very marked absorption peaks (> 0.6), each corresponding to a granular discontinuity. Thus, by deliberately modulating the particle size curve of the mix, it is possible to target one or more particular frequencies of the noise to be absorbed, depending on the type of noise present in the environment of the mix.

Claims

1. Acoustic pavement for a taxiway comprising at least one binder, preferably a bituminous binder, and aggregates comprising several granular fractions d / D, each defined by a lower caliber (d), an upper caliber (D) and a median dm; characterized in that the distribution of the granular fractions of the aggregates is such that: i. for at least a portion of the so-called continuous granular fractions, on the one hand, the medians progressively increase from a fraction da / D "of smaller median dma, followed by a fraction dp / Dp, to a fraction d®, and on the other hand, the mass ratios Rm of these fractions, defined with respect to the total weight of the aggregates, are also progressing progressively from the smaller fraction of 7Da. median dm ", up to the fraction d® / D® of greater median dm®, the ratio RrriVRin15 being greater than or equal to 2, preferably to 3, and more preferably still to 4; ii. at least two other granular fractions, called rupture fractions, are each inserted between two continuous granular fractions, these granular fracture fractions being respectively da / Da of median dma and db / Db of median dmb greater than dma, the mass ratio of each fracture fractions being lower than the mass ratio of the previous continuous fraction, and the granular fraction da / Da of median dma between the fraction da / D "and the second continuous fraction dc / Dc has a mass ratio Rma less than rm "

2. Acoustic coating according to claim 1, characterized in that the upper caliber Da of the continuous fraction d ° 7D "is equal to the lower caliber da of the fracture fraction da / Da.

3. Acoustic mix according to one of the preceding claims, characterized in that the ratio between the mass ratio of each of the granular fracture fractions relative to its relative width is such that:

preferably 0.3, and even more preferably 0.2; and

preferably 0.4, and even more preferably 0.3.

4. Acoustic coating according to one of the preceding claims, characterized in that the continuous fraction da / D "has a higher gauge D" determined according to the standard NF EN 933-1, less than or equal to 4 mm, preferably 2 mm and even more preferably 63 μm.

5. Acoustic coating according to one of the preceding claims, characterized in that the fracture fraction da / Da has on the one hand a lower caliber da greater than or equal to 63 μηι and on the other hand, a higher caliber Da higher or equal to 4 mm, preferably 2 mm, and even more preferably 1 mm, as determined according to standard NF EN 933-1.

6. Acoustic coating according to one of the preceding claims, characterized in that the continuous fraction d® / D® defined by the median dm® has an upper D® caliber less than or equal to, in an increasing order preferably 25 mm, 14 mm, 10 mm, 6 mm.

7. Acoustic coating according to one of the preceding claims, characterized in that the mass ratio of the continuous fraction d® / D® is greater than or equal to 50% by weight, preferably 60% by weight, more preferably 70% by weight. % by weight relative to the total aggregates.

8. Acoustic coating according to one of the preceding claims, characterized in that it has after compaction a void percentage greater than or equal to 20%, preferably 25%, even more preferably 30%, defined according to EN 12697- 8 or the EN 12697-31 standard with 25 gyrations.

9. Acoustic coating according to one of the preceding claims, characterized in that it has a percentage of rut depth 10,000 cycles, measured according to the standard 12697-22 at 60 ° C, less than or equal to 10%, preferably 7.5%, and even more preferably 5%.

10. Acoustic coating according to one of the preceding claims, characterized in that it has an acoustic absorption coefficient whose values include at least two local maxima (absorption peaks) greater than 0.6 or 0.7, preferably 0.8, still more preferably 0.9, over a frequency range between 40 and 4000 Hz, and measured according to the NF standard in ISO 10534-2 / 2003.

11. Acoustic coating according to one of the preceding claims, characterized in that the binder content is less than or equal to 5.5% by weight, preferably 5%, even more preferably 4.7%, and more particularly 4, 5%.

12. Acoustic coating according to one of the preceding claims, characterized in that the binder is a modified bitumen, preferably by an agent selected from the group comprising, ideally constituted by: natural rubbers, synthetic polymers, compounds organometallic compounds, sulfur and sulphides, adhesiveness dopes, and mixtures thereof.

13. A method of manufacturing an acoustic mix according to one of claims 1 to 12 comprising the following steps: a- choose classes of aggregates d / D so that distribution of granular fractions after mixing is as defined in the claim 1, b- optionally selecting at least two target acoustic absorption frequencies for the asphalt mix and choosing the aggregates classes d / D such that the granular fracture fractions obtained after mixing allow the coincidence of the absorption peaks ( measured according to standard NF EN ISO 10534-2 of 2003) with the target acoustic absorption frequencies according to the thickness of implementation aimed, c- to mix the aggregates in order to obtain a homogeneous whole, d- to add a binder, preferably a bituminous binder, e-mix the aggregates with the binder.

14. Route of circulation comprising at least one layer of acoustic mix according to any one of claims 1 to 12, said layer preferably being an upper layer of pavement, and even more preferably a wearing course.

15. Route of circulation according to claim 14, characterized in that it comprises a surface layer comprising at least two superimposed sub-layers, including a rolling upper layer and a lower bonding sub-layer, at least one said sub-layers being based on at least one mix according to any one of claims 1 to 12.